Progressive power lens

Abstract

PCT No. PCT/JP91/01759 Sec. 371 Date Aug. 25, 1992 Sec. 102(e) Date Aug. 25, 1992 PCT Filed Dec. 25, 1991 PCT Pub. No. WO92/12452 PCT Pub. Date Jul. 23, 1992.In the present invention, the distance, the intermediate, and the reading portions are smoothly jointed together, and thereby the present invention provides a progressive power lens which is capable of enlarging an area, which provides an excellent field of view, by improving aberration of the lens body as well as reducing in weight and thickness. The curvature of one of two refracting interfaces of the distance portion or the reading portion varies along the principal gazing line from the vicinity of the center of the lens toward the peripheral portion thereof, the refracting interfaces oppositely facing to each other.

What is claimed is: 
     
       1. A progressive power lens comprising a distance portion (1) having a positive refractive power for looking at a location at a relatively long distance, a reading portion (2) for looking at a location at a relatively short distance, and an intermediate portion (3) between the distance portion and the reading portion for looking at a location at a relatively intermediate distance, the curvature of at least one of the oppositely facing refracting surface of the distance portion being reduced in curvature along a principal gazing line (4) of the lens at a substantially constant rate from the vicinity of the center of the lens to the peripheral portion thereof, the one refracting surface being on side of an object. 
     
     
       2. A progressive power lens as recited in claim 1, wherein the curvature of the distance portion (1) has a constant value at an interval of at least 12 mm from the vicinity of the center to the peripheral portion of the distance portion, and then changes. 
     
     
       3. A progressive power lens as recited in claim 1, characterized in that a plastic material having a refractive index of not smaller than 1.55 is used. 
     
     
       4. A progressive power lens comprising a distance portion (1) having a positive refractive power for looking at a location at a relatively long distance, a reading portion (2) for looking at a location at a relatively short distance, and an intermediate portion (3) between the distance portion and the reading portion for looking at a location at a relatively intermediate distance, the curvature of at least one of the oppositely facing refracting surfaces of the distance portion being increased in curvature along a principal gazing line (4) of the lens at a substantially constant rate from the vicinity of the center of the lens to the peripheral portion thereof, the one refracting surface being on the side of an eye ball. 
     
     
       5. A progressive power lens comprising a distance portion (1) having a negative refractive power for looking at a location at a relatively long distance, a reading portion (2) for looking at a location at a relatively short distance, and an intermediate portion (3) between the distance portion and the reading portion for looking at a location at a intermediate distance, the curvature of at least one of the oppositely facing refracting surface of the distance portion being increased in curvature from the vicinity of the center of the lens to the peripheral thereof, the one refracting surface being on the side of an object. 
     
     
       6. A progressive power lens as recited in claim 5, wherein the distance portion (1) has a negative refractive power, one refracting surface (8) of the two oppositely facing refracting surfaces is reduced in curvature after once increased, the one refracting surface being on the side of an object. 
     
     
       7. A progressive power lens comprising a distance portion (1) having a negative refractive power for looking at a location at a relatively long distance, a reading portion (2) for looking at a location at a relatively short distance, and an intermediate portion (3) between the distance portion and the reading portion for looking at a location at a relatively intermediate distance the curvature of at least one of the oppositely facing refracting surfaces of the distance portion being reduced in curvature from the vicinity of the center of the lens to the peripheral portion thereof, the one refracting surface being on the side of an eye ball. 
     
     
       8. A progressive power lens as recited in claim 7, wherein the distance portion (1) has a negative refractive power, one refracting surface (9) of the two oppositely facing refracting surfaces increases in curvature after once reduced, the one refracting surface being on the side of an eye ball. 
     
     
       9. A progressive power lens comprising a distance portion (1) for looking at a location at a relatively great distance, a reading portion (2) for looking at a location at a relatively short distance, and an intermediate portion (3) between the distance portion and the reading portion for looking at a location at a relatively intermediate distance, the curvature of at least one of the oppositely facing refracting surfaces of the reading portion (2) changes along a principal gazing line (4) of the lens from the vicinity of the center to a peripheral portion of the lens. 
     
     
       10. A progressive power lens as recited in claim 9, characterized wherein one refracting surface (8) of the two oppositely facing refracting surfaces is reduced in curvature at a substantially constant rate from the vicinity of the center of the lens to the peripheral portion thereof, the refracting surface being on the side of an object. 
     
     
       11. A progressive power lens as recited in claim 9, wherein one refracting surface (9) of the two oppositely facing refracting surfaces increases in curvature at a substantially constant rate from the vicinity of the center of the lens to the peripheral portion thereof, the one refracting surface being on the side of an eye ball. 
     
     
       12. A progressive power lens as recited in claim 10, wherein the curvature of the reading portion (2) has a constant value at an interval of at least 7 mm from the vicinity of the center to the peripheral portion of the reading portion, and then changes. 
     
     
       13. A progressive power lens which has a prescription for correcting myopia in the distance portion region, characterized in that a prism, having a magnitude Pt, is provided with a base in the direction of 90°, the prism having no object to cure strabismus, the Pt satisfying the following relationship: ##EQU3## where PW is the prescription for correcting myopia and ADD is an addition power.